Sleep More To Get Fitter – Mental Fatigue Affects Exercise Intensity

If you sometimes feel that you are not exercising as hard as usual then your lack of physical exertion while training could be due to mental fatigue. Sports scientists found that being tired, or suffering from mental fatigue, reduces your ability to exercise at higher levels of intensity.

Researchers from Bangor University found that when athletes became tired their performance reduced. However, the reduction in performance, or exercise intensity, was not as a result of a reduction in efficiency of the cardiovascular system, but as a result of simply being tired.

“our study provides experimental evidence that mental fatigue limits exercise tolerance in humans through higher perception of effort rather than cardiorespiratory and musculoenergetic mechanisms.” Marcora et al.

The research compared a group of subjects who exercised immediately after 90 minutes of demanding cognitive tasks with a group who had spent 90 minutes relatively relaxed, but awake.

In a questionnaire after the exercise sessions the mentally fatigued subjects considered the intensity of the exercise to be significantly higher than it actually was. The subjects that were relatively relaxed before exercising were able to work harder, even though physically they were not in any better shape.

“The main finding of our experimental study is that mental fatigue impairs physical performance, which was measured as time to exhaustion during high-intensity cycling exercise.”

For both groups of subjects the maximum intensity at which they could exercise was actually the same, however, in the mentally tired group they were not able to sustain intensity for so long. Time to exhaustion was significantly lower in the mentally fatigued group.

Prior to this research it was assumed that the ability to perform carry out short term intense exercise was determined by the fitness levels of a person alone, however, the research shows that the mental state of a person makes a big difference.

This research is not only relevant to athletes and sports players (footballers – those late nights partying really do affect your performance on the pitch) but to anyone that wants to get fit and lose weight.

Research has shown that the best way to get fit is to perform more intensive exercise, but if you are always exercising when you are mentally tired, such as after a long day in the office, then you will not be making the maximum progress that you are physically capable of because you will not be working to the highest intensity. Basically, you cannot give it 100% if you are tired.

Take A Power Nap Before Power Training

A power nap before you exercise could make all the difference. If you have had a really busy day then 15 minutes sleep (no more) followed by a black coffee could give your mind the boost it needs to allow you to work harder at improving your fitness, strength and performance. Give you mind time to wind down and relax before you start exercising.

If you have a stressful job then your lunch hour may not be the best time to exercise if you are keen to make the biggest fitness and strength gains. However, the exercise will help to reduce stress.


Mental fatigue impairs physical performance in humans” by Samuele M. Marcora, Walter Staiano, and Victoria Manning. Journal of Applied PhysiologyMarch 2009 vol. 106 no. 3857-864. Full text.

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